The research presented in this chapter explores, using examples from an earlier version of the Swedish Scholastic Aptitude Test [the SweSAT], the possible environmental influence on cognitive test performance with respect to the effects of differences in earlier education. Relatively large differences in results between students having attended different tracks of study in upper secondary school have been noticed in the SweSAT. Obviously, this may be due to initial differences when entering these tracks. However, it may also be assumed that different tracks followed in the upper secondary schooling may influence abilities measured by the SweSAT in a different manner. The present study tentatively proposes the effects of track of study both on the observed results in a set of sub-tests and on certain ability factors previously proposed to lie behind performance on the test, after control for marks, at the end of lower secondary education.